Acoustic mode propagation in a range-dependent ocean

Desaubies, Yves; Chiu, Ching‐Sang; Miller, James H.

doi:10.1121/1.393805

Cited by 17 publications

(11 citation statements)

References 14 publications

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“…Desaubies et al 1986 have actually shown that the adiabatic approximation breaks down even sooner than predicted by the above condition because of improperly accounting for modal phases.…”

Section: Range-dependent Normal Mode Theorymentioning

confidence: 96%

Analysis of acoustic propagation in the region of the New England continental shelfbreak

Sperry¹

1999

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During July and August of 1996, a large acoustics/physical oceanography experiment was fielded in the Mid-Atlantic Bight, south of Nantucket Island, MA. Known as the Shelfbreak Front PRIMER Experiment, the study combined acoustic data from a moored array of sources and receivers with very high resolution physical oceano graphic measurements. This thesis addresses two of the primary goals of the exper iment, explaining the properties of acoustic propagation in the region, and tomo graphic inversion of the acoustic data. In addition, this thesis develops a new method for predicting acoustic coherence in such regions.Receptions from two 400 Hz tomography sources, transmitting from the continen tal slope onto the shelf, are analyzed. This data, along with forward propagation modeling utilizing SeaSoar thermohaline measurements, reveal that both the shelfbreak front and tidally-generated soliton packets produce stronger coupling between the acoustic waveguide modes than expected. Arrival time wander and signal spread show variability attributable to the presence of a shelf water meander, changes in frontal configuration, and variability in the soliton field. The highly-coupled nature of the acoustic mode propagation prevents detailed tomographic inversion. Instead, methods based on only the wander of the mode arrivals are used to estimate pathaveraged temperatures and internal tide "strength".The modal phase structure function is introduced as a useful proxy for acoustic coherence, and is related via an integral transform to the environmental sound speed correlation function. Advantages of the method are its flexibility and division of the problem into independent contributions, such as from the water column and seabed.

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“…Desaubies et al 1986 have actually shown that the adiabatic approximation breaks down even sooner than predicted by the above condition because of improperly accounting for modal phases.…”

Section: Range-dependent Normal Mode Theorymentioning

confidence: 96%

Analysis of acoustic propagation in the region of the New England continental shelfbreak

Sperry¹

1999

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“…Also belonging to this first class of solutions to the range-dependent problem is the work of Desaubies, Chiu, and Miller [11]. In their 1986 study these authors set out to quantify when it is appropriate to make the adiabatic approximation in the context of slow changes to the sound-speed structure of the ocean due to mesoscale eddies.…”

Section: Previous Workmentioning

confidence: 99%

Asymptotic stepwise coupled modes for horizontally-variable acoustic media

White

Clark

Potty

et al. 2017

The Journal of the Acoustical Society of America

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Efficient and accurate mathematical codes for the prediction of underwater sound propagation are a critical component of SONAR system development and operation. Shallow water provides a unique set of complications to the problem of acoustic propagation prediction due to range dependence of acoustic properties resulting from a high number of wave interactions with the surface and seafloor and bathymetric variation. In this situation, the modes of vibration of the acoustic wave equation become coupled, with a transfer of energy between adjacent modes occurring upon traversing a horizontal change of environment. While mode methods have been developed for solving this range-dependent problem with varying accuracy, the computational intensity of these solutions makes them unsuitable for use in applications where real-time or near real-time performance is desired.The goal of the research presented herein was to develop, implement, and verify an efficient and rigorous coupled-mode solution for acoustic wave propagation in shallow water range-dependent environments. Particular interest was given to developing a solution that maintains analytical integrity while executing in a time window that is useful for tactical applications. A theoretical framework involving a range-expanded inner product for capturing the coupling between modes as they propagate through a horizontally-variable medium is presented. This framework includes a novel discretization of the range-dependent acoustic medium. A difference equations approach, which implements the inner product to account for non-adiabatic energy transfer between modes, is used to recursively compute reflection and transmission coefficients throughout the discretized environment.Increased efficiency is gained in the method due to the ability to compute coupling via closed-form algebraic expressions and in the application of asymptotic analysis to simplify the transmission and reflection coefficient solutions. ACKNOWLEDGMENTS

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“…In coupled propagation, energy is exchanged between the local modes due to range variations in bathymetry and sound speed [24), [25] .…”

Section: Normal Mode Model For Acoustic Propagationmentioning

confidence: 99%

“…Desaubies [25] quantified measures indicating t he importance of modal coupling in an environment. He found that t he precise conditions when the adiabatic approximation breaks down depends on the quantity of interest, i.e., pressure, transmission loss, propagation time, etc .. .…”

Section: Normal Mode Model For Acoustic Propagationmentioning

confidence: 99%